Thermal cycling apparatus and method

ABSTRACT

A thermal cycling apparatus having a sample interfacing wall extending from a mounting wall. The sample interfacing wall can accept and apply thermal cycles to samples. An air source can direct an air stream to cool the sample. Another source can direct heated air away from the sample.

This application is a U.S. National Phase of International ApplicationNo. PCT/US2013/041231, filed May 15, 2013, which claims priority to U.S.Provisional Patent Application No. 61/647,493, filed on May 15, 2012,the disclosures of which are incorporated by reference.

BACKGROUND OF THE INVENTION

Various biological testing procedures require thermal cycling, generallyto cause a chemical reaction via heat exchange. One example of such aprocedure is polymerase chain reaction (PCR) for DNA amplification.Further examples include isothermal nucleic acid amplification,rapid-PCR, ligase chain reaction (LCR), self-sustained sequencereplication, enzyme kinetic studies, homogeneous ligand binding assays,and more complex biochemical mechanistic studies that require complextemperature changes.

Such procedures require a testing system that can accurately raise andlower sample temperatures with precision, and in some cases rapidity.Many such systems exist, which typically use cooling devices (e.g.,fans) that occupy a large amount physical space and require significantpower to provide a required amount of performance (i.e., a rapidtemperature drop). Further, such cooling devices have issues withstart-up lag time and shut-down overlap, that is, will function afterbeing shut off, and thus do not operate with instantaneous digital-likeprecision. For example, a centrifugal fan will not instantly blow atfull volumetric capability when turned on and will also continue torotate after power is shut off, thus implementing overlap time that mustbe accounted for in testing. Such issues typically get worse with deviceage.

The low cost of such cooling devices, relatively acceptable performance,and easy implementation has prevented industry from answering theseissues. The answer thus far, has been to incorporate more powerful fanshaving greater volumetric output rates, which also increase space andpower requirements. One price of this is a negative effect onportability of field testing systems, which can be used, for example, torapidly detect viral outbreaks in outlying areas. Accordingly, there isan unanswered need to address the deficiencies of known cooling devicesused in biological testing systems.

BRIEF SUMMARY OF THE INVENTION

One embodiment of the invention relates to a thermal cycling apparatusthat may include a mounting wall partially defining a chamber forthermally cycling biological samples. The mounting wall may have a firstmounting surface opposing a second mounting surface. A sampleinterfacing wall can transversely extend from the second mountingsurface. The sample interfacing wall may have a planar interfaceaccessible from the second mounting surface. The sample interfacing wallmay include a first heating element and a second heating element onopposing sides of the planar interface. A first air source can have anexit arranged to direct air at the first heating element. A second airsource can have an exit arranged to direct air away from the firstheating element. A third air source can have an exit arranged to directair at the second heating element. A fourth air source can have an exitarranged to direct air away from at the second heating element.

In some embodiments, each air source includes an air pump having aplanar face, the exit being on the planar face, and a plurality of edgessurrounding the planar face.

In some embodiments, each air pump may be coupled to the second mountingsurface such that its planar face is substantially transverse to thesecond mounting surface.

In some embodiments, the first air pump, second air pump, and sampleinterfacing wall may be arranged to define a first sub-volume of thechamber.

In some embodiments, the exit of the second air pump can be arranged topush air out of an exit of the first sub-volume.

In some embodiments, the third air pump, fourth air pump, and sampleinterfacing wall can be arranged to define a second sub-volume of thechamber.

In some embodiments, the exit of the fourth air pump can be arranged topush air out of an exit of the first sub-volume.

In some embodiments, the first and third air sources can be eacharranged to direct respective air streams directly at the first andsecond heating elements.

In some embodiments, the second and fourth air sources can be eacharranged to direct an air stream at the sample interfacing wall.

In some embodiments, the second and fourth air sources can be eacharranged to direct an air stream along the sample interfacing wall.

In some embodiments, the second and fourth air sources are each arrangedto suction air away from the sample interfacing wall.

In some embodiments, the mounting wall and sample interfacing wall caninclude printed circuit boards.

In some embodiments, the sample interfacing wall can divide the chamberinto substantially equal volumes.

In some embodiments, the air sources can be symmetrically positionedabout the sample interfacing wall.

In some embodiments, each air source can include a planar housing havingan internal piezoelectric element mounted to an internal diaphragm.

In some embodiments, each planar housing can include an exit port, andthe exit ports of the first and third air sources can be arranged todirectly provide respective air streams at the first and second heatingelements.

In some embodiments, the exit ports of the second and fourth air sourcescan be arranged to provide respective air streams along or away from thesample interfacing wall.

Another embodiment of the invention relates to a thermal cycling method.In the method, a first heating element and a second heating element canbe activated, each heating element being positioned adjacent to abiological sample holder. Using a first air source, a first air streamcan be directed at a first heating element to transfer heat from thefirst heating element. Using a second air source, a second air streamcan direct heated air away from the first heating element. Using a thirdair source, a third air stream can be directed at a second heatingelement to transfer heat from the second heating element. Using a fourthair source, a fourth air stream can direct heated air away from thefirst heating element.

In some embodiments, the first and second heating elements arepositioned on opposed sides of a sample interfacing wall, and the sampleinterfacing wall may extend from a mounting surface.

In some embodiments, the air sources each can include substantiallyplanar housings edge mounted to the mounting surface.

In some embodiments, the first and third air streams can directlyintersect the first and second heating elements.

In some embodiments, the second and fourth air streams can be directedalong the sample interfacing wall.

In some embodiments, the second and fourth air streams can be directedaway from the sample interfacing wall.

In some embodiments, each air source can include a planar housing havingan internal piezoelectric element mounted to an internal diaphragm.

In some embodiments, each air stream can be directed by powering eachpiezoelectric element.

In some embodiments, the piezoelectric elements can be powered ON andOFF according to a predetermined cooling cycle.

In some embodiments, the heating elements can be powered ON and OFFaccording to a predetermined heating cycle, with the ON portion of theheating cycle being out of phase with the ON portion of the coolingcycle.

In some embodiments, temperatures of the first and second heatingelements may be monitored.

In some embodiments, the first and second heating elements can beactivated to provide heat to the biological sample holder according to apredetermined minimum temperature and a predetermined maximumtemperature.

In some embodiments, the air sources may be controlled to direct airwhen the biological sample holder reaches the predetermined maximumtemperature.

In some embodiments, the air sources are controlled to stop directingair when the biological sample holder reaches the predetermined minimumtemperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified schematic drawing of a testing system 100,according to some embodiments of the invention.

FIG. 2A is a perspective view of a thermal cycling device, according tosome embodiments of the invention.

FIG. 2B is a front view of the thermal cycling device of FIG. 2A.

FIG. 2C is a rear view of the thermal cycling device of FIG. 2A.

FIG. 2D is a top view (downward facing) of the thermal cycling device ofFIG. 2A.

FIG. 2E is a bottom view (upward facing) of the thermal cycling deviceof FIG. 2A.

FIG. 2F is a side view of the thermal cycling device of FIG. 2A.

FIG. 2G is the side view of FIG. 2F with components removed for clarity.

FIG. 2H is a simplified rear view of the thermal cycling device of FIG.2A in use, according to some embodiment of the invention.

FIGS. 3A-3E are rear views of thermal cycling devices, according torespective embodiments of the invention.

FIG. 4A is a cross-sectional view of an air source, according to someembodiments of the invention.

FIG. 4B is a cross-sectional view of a plurality of linked pressurizedair sources, according to some embodiments of the invention.

FIGS. 5A-5E are various schematical diagrams of arrangements ofpluralities of linked pressurized air sources, according to someembodiments of the invention.

FIG. 5F is a simplified rear view of a variation of the thermal cyclingdevice of FIG. 2A, having pluralities of linked pressurized air sources,in use, according to some embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

I. System Overview:

FIG. 1 shows a simplified schematic drawing of a system 100 for testinga sample. The system 100 includes a sample cartridge 110, which isconfigured for receiving and holding a sample of material, such as abodily fluid (e.g., blood, urine, salvia) or solid (e.g., soil, spores,chemical residue) that is liquid soluble. The sample cartridge 110 canbe a walled structure having one or more fluid channels and connectionports. The sample cartridge 110 may be relatively small, such that itcan be easily be hand-held, portable, and/or disposable. An example ofsuch a cartridge (useable with the system 100) is disclosed in U.S. Pat.No. 6,660,228, which is incorporated by reference herein.

The sample cartridge 110 can hold one or more reagents and/or chemicalsthat are used to process a sample, in order to ultimately detect someproperty of the sample. One example of such a process is PCR, which isused to amplify the presence of DNA. The sample cartridge 110 caninclude a sample chamber 110 a, which is where the sample can besubjected to thermal cycling.

The sample cartridge 110 can interface with a thermal cycling module120, such that the sample chamber 110 a is thermally coupled thereto.The thermal cycling device 120 includes one or more apparatuses 120 aconfigured to deliver energy to, and also remove energy from, the samplechamber 110 a. Accordingly, at least one apparatus 120 a, such as anelectric heater, of the thermal cycling apparatus 120 a can deliver heatto the sample chamber 110 a, and at least one more apparatus 120 b, cancool the sample chamber 110 a to remove the heat. Such heating andcooling can be performed in a cyclic manner.

A sample preparation module 130 also interfaces with the samplecartridge 110. The sample preparation module 130 is configured toprocess the sample within the sample cartridge 110 before and/or afterthe sample is thermally cycled. The module 130 can include one or moredevices to affect movement of the sample within the cartridge 110. Forexample, one device 130 a can connect to a port of the cartridge inorder to supply a negative or positive pressure, which can be used tomove the sample to different portions of the cartridge 110, such as thesample chamber 110 a. Such a device could be a vacuum pump or a plunger,or an electric motor used to power a sample movement mechanism withinthe sample cartridge 110. Another device 130 b of the module 130 mayapply energy to the sample, e.g., ultrasonic vibration, in order tophysically disrupt the sample into a simpler form and/or affect achemical reaction with one or more reagents and/or chemicals. Such adevice could incite vibration via a piezoelectric device.

A sensor module 140 also interfaces with the sample cartridge 110. Thesensor module 140 may include one or more sensors 140 a and circuits 140b configured to generate signals based on detectable properties of thesample. These signals can be processed to ultimately provide usefuldata. For example, the sensor module 140 may include a detector and anenergy source for providing electromagnetic energy to the sample inorder to cause a reaction, detect an absorbance of the energy, or detectan excitation caused by the energy. A sensor 140 a can be opticallybased, and include one or more cameras, such as a CCD.

The thermal cycling device 120, sample preparation module 130, andsensor module 140 can be physically and/or electrically integrated withone another, wholly or in-part. For example, these aspects can be housedwithin a greater testing module 150, which is configured specificallyfor one or more processes. The testing module 150 can be physicallyimplemented within a multi-walled structure, such as a portable modularhousing, and further include a controller 160. The controller 160 isconfigured to provide the thermal cycling device 120, sample preparationmodule 130, and/or sensor module 140, with control commands based onelectrical inputs received from the modules.

The testing module 150 can interface with a computing module 160. Insome embodiments, the testing module 150 receives power and commandsexclusively from the computing module 160. Conversely, in otherembodiments, the testing module may be self-powered (e.g., via aninternal battery) and/or locally powered (e.g., via a wall outletconnection), and have a memory device configured to store testingresults from the sensor module 140 for later delivery to the computingmodule 160. In such embodiments, the power and memory aspects can beincorporated as sub-aspects of the sensor module 140. Yet, in furtherembodiments, the testing module can be independently powered (e.g.,battery, wall plug) but reliant on the computing module 160 to receivecontrol commands via a direct (e.g., wired) or indirect (e.g., wireless)connection.

The computing module 160 can be a general purpose computer, specialpurpose computer, server, or cluster of servers. Generally, thecomputing module 160 includes at least one processor, connected by acommunications bus to various types of physical memory (e.g., RAM,processor cache, HDD) and input/output devices (e.g., keyboard,monitor). Methods for operating the testing module 160 can be stored,permanently or as operationally needed, as machine readable instructionsin the various types of memory. Accordingly, the processor can executethe instructions to perform the methods.

II. Thermal Cycling Module:

FIGS. 2A-2G shows a thermal cycling device 200, which is an embodimentof thermal cycling device 120.

The thermal cycling device (TCD) 200 is a modular component forcyclically providing heat and cooling to a testing sample. The TCD 200includes a chamber 202 partially defined by a mounting wall 204, whichalso serves as a support for component mounting. The mounting wall 204can be integrated with a greater enclosure, such as the testing module150. The mounting wall 204 can be constructed of one or more layers ofrigid material, such as aluminum, steel, or plastic. The mounting wall204 can include a first mounting surface 206, that can be readilyaccessed for insertion of a sample cartridge. The second mountingsurface 208 can be a portion of a structural member, such as a portionof sheet metal or molded plastic. The mounting wall 204 can also includea second mounting surface 208, which is generally inwardly facing andnot readily accessible by a user. The second mounting surface 208 can bea portion of a PCB board having traces for supplying electric signals todevices mounted thereto.

Extending transversely from the second mounting surface 208 is a sampleinterfacing wall 210. The sample interfacing wall 210 can be a PCB boardin electrical communication with the mounting wall 204. The sampleinterfacing wall 210 provides a support structure for a planer interface212. The planar interface 212 is a specialized female connector thatextends into the sample interfacing wall 210. The planar interface 212includes two planar heating elements 214 opposing one another, with anopen space therebetween configured to receive a male connector.

The planar interface 212 also includes sensors which are configured todetect aspects of the sample through edges of the male connector. Thisarrangement is well shown in FIG. 2G. The male connector includes aplanar sample chamber (e.g., of sample cartridge 110) that is insertedinto the planar interface 212. The planar heating elements 214 eachprovide a relatively large surface area (e.g., 170 mm² each) to transferheat to corresponding planar sides of the planar sample chamber, each ofwhich can have a comparatively smaller surface area (e.g., 16 mm² each).

A plurality of air sources can be coupled, directly or indirectly, tothe second mounting surface 208 and/or the sample interfacing wall 210.In some embodiments, the plurality of air sources includes a first airsource 216 a, second air source 216 b, third air source 216 c, and afourth air source 216 d.

As shown, the first air source 216 a is positioned on one side of thesample interfacing wall 210, such that a planar face 218 a of the firstair source 216 a is arranged to be substantially parallel with thesample interfacing wall 210. In some embodiments, the first air source216 a and sample interfacing wall 210 are separated by a distance ofapproximately 9.5 mm. The second air source 216 b is positioned suchthat a planar face 218 b, or a virtual planar extension thereof, of thesecond air source 216 b intersects with the sample interfacing wall 210such that an acute angle is present therebetween, which here is shown tobe approximately 45°. A third air source 216 c and a fourth air source216 d are likewise positioned on the other side of the sampleinterfacing wall 210.

The arrangement of the air sources 216 is shown to be substantiallysymmetrical about the sample interfacing wall 210. However, symmetry isnot required, and thus an asymmetric arrangement is also possible.Further, in some embodiments the third air source 216 c and a fourth airsource 216 d are not present. In other embodiments, only the first airsource 216 a and fourth air source 216 d are present.

The second air source 216 b and the third air source 216 c can beconnected to the sample interfacing wall 210 by elongated supports 220a, which are affixed to the sample interfacing wall 210. The elongatedsupports 220 a can each include a trough configured to hold an edge ofan air source 216. Likewise, the first and fourth air sources 216 a/216d can be connected to the second mounting surface 208 via elongatedsupports 220 b, which can each include a trough configured to hold anedge of an air source. Accordingly, as shown each air source 216 isdirectly or indirectly “edge mounted” to the sample interfacing wall 210and second mounting surface 208, such that the planar face of each airsource 216 is substantially transverse to the second mounting surface208.

Extents of the sample interfacing wall 210 and the second mountingsurface 208 partially define a chamber of the system 100, as shown bythe dashed lines in FIG. 2A. Put another way, the chamber is a volumethat is at least determined by area of the second mounting surface 208multiplied by the extension length of the sample interfacing wall 210from the second mounting surface 208. The first air source 216 a, secondair source 216 b, second mounting surface 208, and sample interfacingwall 210 partially define a first sub-volume V1 within the chamber.Likewise the third air source 216 c, fourth air source 216 d, secondmounting surface 208, and sample interfacing wall 210 partially define asecond sub-volume V2 within the chamber.

The first air source 216 a and fourth air source 216 d are arranged suchthat corresponding exit ports 222 a/222 d on planar faces 218 a/218 ddirectly point at planar heating elements 214 on the planar interface212. Air inlets are also generally provided on each air source 216opposite to the exit ports 222. Accordingly, air streams exiting theexit ports 222 a/222 d are vectored to intersect the planar heatingelements 216 of the planar interface 212, to affect a sample chamber ofa connected cartridge. The second air source 216 b and third air source216 c are arranged such that corresponding exit ports 222 a/222 ddirectly point at positions on the sample interfacing wall adjacent toor at the same location ports 222 a/222 b are directed to. Accordingly,air streams exiting the exit ports 222 b/222 c are vectored to intersectthe sample interfacing wall at an acute angle, i.e., less than 90°. Asshown, the angle of intersection for exit ports 222 b/222 c isapproximately 45°.

In use, the TCD 200 can rapidly thermally cycle a sample held by theplanar interface 212 between relatively low and high temperatures. Thesample will be brought from a high or low temperature to a low or hightemperature, which is performed by one or more controllers operating theplanar heating elements 214 and cooling performed by the air sources216. Thermal cycling is required for some biological testing processes,such as PCR. For PCR, a sample will typically be held at a lowtemperature of 60° C. for a predetermined amount of time and ramped upto a high temperature of 94° C. for another predetermined amount oftime. Ramp times, both up and down, between periods of low and hightemperatures are desired to be relatively short compared to sustainedperiods of low and high temperatures. Accordingly, a plot of temperatureover time would ideally resemble a square wave.

Before the thermal cycling process begins, the planar heating elements214 can be powered ON to preheat the sample from an as-deliveredtemperature (e.g., room temperature) to a baseline low temperature(e.g., 60° C.) for a predetermined amount of time (e.g., 6 sec) andsubsequently ramped up to a high temperature (e.g., 94° C.) for apredetermined amount of time (e.g., 6 sec), or alternatively, directlyfrom the as-delivered temperature to the high temperature for apredetermined amount of time.

After the high temperature period is complete, the planar heatingelements 214 are turned OFF, or provided with less power, and the airsources 216 are turned ON to cool the sample and bring the temperatureback to the low temperature for a predetermined amount of time (e.g., 6sec). Once the low temperature period has ended, the air sources 216 arepowered OFF and planar heating elements can once again be powered ONsuch that the sample is ramped back up to the high temperature for apredetermined amount of time. This cycling process continues until apredetermined amount of cycles have been completed. Generally the dutycycles for the planar heating elements 214 and air sources 216 can besubstantially (with minor overlap) out of phase with each other, suchthat the devices are not operating at the same time. However, during thelow and high temperature periods, power to the planar heating elements214 and/or the air sources 216 can be provided as needed (i.e.,intermittently at full/partial power or continuously at partial power),to maintain the sample at the required low or high temperature.

Fluid flow dynamics occurring during the cooling period aresimplistically depicted in FIG. 2H. As shown, the respective planarfaces 218 a/218 d of air sources 216 a/216 d are arranged parallel tothe sample interfacing wall 210 and planar interface 212 (not shown inthis view for clarity), and are emitting air streams from exit ports 222a/222 b that transversely intersect the planar interface 212. Such anarrangement is very effective because it creates turbulent airflow aboutthe planar heating elements 214, which in-turn provides effectivecooling within sub-volumes V1/V2 between the sample interfacing wall 210and the air sources 216 a/216 d.

Thus, it should be understood that the air sources 216 a/216 d are notmerely sources of forced convection, but also structural members thatprovide a confined environment for efficient forced convection heattransfer, thus reducing the overall footprint of the TCD 200 and alsolowering volumetric flow requirements for the air sources 216 a/216 d.Put another way, the farther the air sources 216 a/216 d are from theplanar heating elements 214, the more powerful the air sources 216 a/216d need to be to meet a stated cooling requirement, because air velocitydissipates with increasing distance—the air source arrangement addressesthis by placing forced convection sources relatively close (e.g., 9.5mm) to the planar heating elements 214, thus, the air sources 216 a/216d can have relatively low volumetric flow capability in relation to theheat generated by the planar interface 212, allowing for a compactdesign. Further, the larger the volume that the planar heating elements214 reside in, the more powerful the air sources 216 a/216 d need to beto meet the stated cooling requirement, since the larger volume providesless structure for formation of circulatory eddy currents—the disclosedair source arrangement addresses this by providing the air sources withsurrounding planar faces for turbulent air to circulate.

The air within the sub-volumes V1/V2, however, can quickly becomeheated, and thus cooling efficiency may decrease over one or severalthermal cycles. To help counter this, air sources 216 b/216 c arearranged to direct the heated air out of the sub-volumes V1/ V2 and helpreplenish the sub-volumes V1/V2 with unheated air.

As shown, the respective planar faces 218 b/218 c of air sources 216b/216 c are angularly arranged with respect to the sample interfacingwall 210, such that planar faces 218 b/218 c, or virtual extensionsthereof, intersect with the sample interfacing wall 210 to form acuteangles therebetween. As shown, the air sources 216 b/216 c are emittingair streams from exit ports 222 a/222 b that angularly intersect theplanar interface 212. These air streams work to direct heated air out ofsub-volumes V1/V2 by pushing the heated air out of exits of thesub-volumes V1/V2. Here, air is pushed out towards a bottom direction,along the sample interfacing wall 210, and also a rearward direction(transverse to the mounting wall 204). The air sources 216 b/216 c alsofurther limit the confines of the sub-volumes V1/V2 and thus provide adiscreet air flow paths into and out of the sub-volumes V1/V2.

The embodiment of the TCD 200 shown in FIGS. 2A-2H includes four airsources 216 having a symmetrical arrangement about the sampleinterfacing wall 210. This arrangement is very effective, however, itshould be understood that other beneficial arrangements are alsopossible.

III. Alternative TCD Arrangements:

FIG. 3A shows a TCD 300 having a similar arrangement to TCD 200, withfour air sources 302 a/302 b/302 c/302 d arranged in an almost identicalmanner. Here, TCD 300 differs from TCD 200 in that air sources 302 b and302 c are angularly arranged such that their exit ports face away fromthe interior sub-volumes. Accordingly, air inlets for air sources 302 band 302 c are in direct communication with sub-volumes V1/V2. In use,air sources 302 a/302 d operate as described with reference to TCD 200,however, heated air created within sub-volumes V1/Vs will be divertedinto and out off air sources 302 b and 302 c. Thus, air sources 302a/302 b apply suction to the heated air within sub-volumes V1/V2, whichis replaced with fresh air from the bottom and rearward directions. Insome embodiments, optional top covers 303, covering all or a portion ofthe lateral openings, are used to such that air is primarily drawn intothe sub-volumes V1/V2 from the bottom direction. The dashed lines showthe variable configurations of the top cover. Only one cover 303 isshown for brevity, however, both sides may have a cover 303 oversub-volumes V1/V2.

FIG. 3B shows a TCD 304 having a similar arrangement to TCD 200,however, here only two air parallel sources 302 a/302 d are provided. Insome embodiments, this arrangement is sufficient to provide a requiredlevel of cooling performance, since natural convection will evacuateheated air in the upward direction, and power to the air sources 302a/302 d may also be increased accordingly.

FIG. 3C shows a TCD 306 having a similar arrangement to TCD 200,however, here only two air sources 302 a/302 b are provided, which areasymmetrically arranged to only provide forced convection intosub-volume V1. In some embodiments, this arrangement is sufficient toprovide a required level of cooling performance, and power to the airsources 302 a/302 b may also be increased as needed.

FIG. 3D shows a TCD 308 having a similar arrangement to TCD 200,however, here two additional air sources 302 e/302 f are provided, whichare arranged to apply suction to heated air within sub-volumes V1/V2. Insome embodiments, this arrangement is required to provide a sufficientlevel of cooling performance

FIG. 3E shows a TCD 310 having a similar arrangement to TCD 308,however, here all angularly arranged air sources 302 b/302 c/302 e/302 fare arranged to apply suction sub-volumes V1/V2. In some embodiments,this arrangement is used to provide a sufficient level of coolingperformance. In some embodiments, optional top covers 312, covering allor a portion of the lateral openings, are used to such that air isprimarily drawn into air into the sub-volumes V1/V2 primarily from airsources 302 a/302 d. Further, in some embodiments, the cover mayfluidically seal the sub-volumes V1/V2, such that air sources 302 a/302d provide the only source of fresh air. In such embodiments, this mayincrease the performance of air sources 302 a/302 d by lowering backpressure, since air sources 302 b/302 c/302 e/302 f can be driven tosuction air out at a higher rate than air sources 302 a/302 d canprovide. Thus, the work load on the air sources 302 a/302 d is reduced,which can result in greater volumetric output for a given power input tothe air sources 302 a/302 d. The dashed lines show the variableconfigurations of the top cover. Only one cover 312 is shown forbrevity, however, both sides may have a cover 312 over sub-volumesV1/V2. In some embodiments, top covers 312 may include an additional airsource (shown by the dashed circles) arranged to either provide suctionto or drive air into the sub-volumes V1/V2.

IV. Exemplary Cooling Source:

FIG. 4A shows an example of a cooling source 400 in cross-section. Thecooling source 400 shares the substantially planar construction of theair sources (e.g., 202 a) disclosed herein. The cooling source 400 is anair pump that includes a housing having a planar face 402 surrounded byfour edges or sides 403. In some embodiments, the planar face 402 hasdimensions of 20 mm×20 mm and each edge 403 has dimensions of 1.85 mm×20mm. A piezoelectric device 406 is coupled to an internal diaphragm 404.The diaphragm 404 partially forms an internal pumping chamber 408. Inuse the piezoelectric device 406 is driven to vibrate diaphragm 404.This causes air to be drawn into the pump and evacuated out of nozzle412. The commercially available cooling source is the Microblowermanufactured by Murata Mfg. Co., Ltd., which is rated, at a drivefrequency of 26 KHz, to move 1 L/min at 15 Vpp under 100 Pa of backpressure. In some embodiments the cooling source 400 can be configuredas a high velocity air pump, which in use operates with an internalstatic pressure less than 5 psi. In some embodiments the cooling source400 can be configured as a high pressure air pump, which in use operateswith an internal static pressure greater than 5 psi. The static pressurewithin the internal pumping chamber can be tuned by altering flowresistance where air is drawn in by the diaphragm 404 and/or where airexits at the nozzle 412 and/or at other positions within the coolingsource 400.

FIG. 4B shows an example of a a plurality of linked air sources 414 incross-section. Here, the cooling source is includes at least two coolingsources 400, but may include more. A reservoir 416 is provided betweenthe cooling sources 400 which is fluidly sealed therebetween. In thisconfiguration, the cooling sources 400 are configured as high pressureair pumps. The cooling sources 400 and reservoir 416 are arranged suchthat air resistance from the bottom-most to top-most cooling sourceallows air to flow therebetween.

In testing, cooling sources 400 were arranged as shown in FIG. 3B andwere driven at 24 Vpp, which resulted in a volumetric output rate ofapproximately 1.4 L/min (0.05 CFM) for each cooling source ((total 2.8L/min (0.1 CFM)), assuming a back pressure of approximately 100 Pa. Thisarrangement was found to slightly better the performance of acentrifugal fan (NIDEC GAMMA26 model A333-999) operating at 113 L/min (4CFM) blowing air from the upward direction (with reference to thedirections in FIG. 2A) from a distance of approximately 30 mm. Thecooling sources 400 caused a heat source to drop from 95° C. to 60° C.in 7.5 sec, compared to the fan which took 7.6 sec. Accordingly, theinventive arrangement can at least equal the performance of thecentrifugal fan, while only requiring approximately 2.5% of thecentrifugal fan's volumetric output.

In another test, cooling sources 400 were arranged as shown in FIG. 2C.The cooling sources were driven at 16 Vpp, which resulted in avolumetric output rate of approximately 1.0 L/min (0.035 CFM) for eachcooling source ((total 4 L/min (0.141 CFM)), assuming a back pressure ofapproximately 100 Pa. This arrangement caused a heat source to drop from95° C. to 60° C. in 7.4 sec. Accordingly, this arrangement of coolingsources 400 can at least equal the performance of a centrifugal fan,while only requiring approximately 3.5% of the centrifugal fan'svolumetric output.

In another test, cooling sources 400 were again arranged as shown inFIG. 2C. The cooling sources were driven at 20 Vpp, which resulted in avolumetric output rate of approximately 1.2 L/min (0.042 CFM) for eachcooling source ((total 4.8 L/min (0.17 CFM)), assuming a back pressureof approximately 100 Pa. This arrangement caused a heat source to dropfrom 95° C. to 60° C. in 6.4 sec, which is a 16% improvement over thecentrifugal fan. Accordingly, this arrangement of cooling sources 400can significantly better the performance of a centrifugal fan, whileonly requiring approximately 4.3% of the centrifugal fan's volumetricoutput.

In yet another test, cooling sources 400 were again arranged as shown inFIG. 2C. The cooling sources were driven at 24 Vpp, which resulted in avolumetric output rate of approximately 1.4 L/min (0.05 CFM) for eachcooling source ((total 5.6 L/min (0.2 CFM)), assuming a back pressure ofapproximately 100 Pa. This arrangement caused a heat source to drop from95° C. to 60° C. in 5.8 sec, which is a 26% performance improvementversus the centrifugal fan. Accordingly, this arrangement of coolingsources 400 can significantly better the performance of a centrifugalfan, while only requiring approximately 5% of the centrifugal fan'svolumetric output.

From these tests, it is evident that embodiments of the invention canequal or better the performance of a centrifugal fan. The centrifugalfan requires a relatively large operating environment given its physicalsize (approximately 50 mm×50 mm×15 mm), while embodiments of theinvention add virtually no space requirements to a test system. Thus,size, power, and cooling efficiencies can be optimized using embodimentsof the TCD. Further, the TCD provides much better response times, sinceexcitation of the piezoelectric devices are near instantaneous.

FIGS. 5A-5E show schematically diagrams different diagrams ofarrangements of pluralities of linked pressurized air sources(“stacks”), according to some embodiments of the invention. In someembodiments, a stack can be configured to provide impingement cooling,which is a high pressure air stream. Impingement cooling can beeffective at removing a boundary layer of hot “sticky” air thateffectively sticks a heat source. In some embodiments, a stack can beconfigured to have an inlet/outlet pressure ratio of 0.54. In someembodiments, a stack can be configured to provide a pulsed air stream,with pulses delivered approximately every 1.6 seconds. A stack generallyrequires at least two pressurized air sources fluidly linked in series,however, more (e.g., 1-10) may be used. Each pressurized air source canadd 5 psi of pressure to the air that provided to its inlet. Forexample, a downstream pressurized air source can be provided with air at5 psi by an upstream pressurized air source, and thus provide 10 psi ofair. Generally, the number of pressurized air sources is only limited byair flow, that is, at a certain point air resistance will simply becometoo great so as to prevent air movement within the stack.

In FIG. 5A a first and second stack are arranged to laterally andtransversely direct air at a heat source. FIG. 5B shows a stackconfiguration having more than two linked cooling sources arranged inseries. FIG. 5B also shows a stack configuration having a plurality ofcooling sources linked in parallel providing air to a single coolingsource. FIG. 5C shows a combination of the configurations of FIG. 5B.FIG. 5D shows stack configurations with valves regulating flow into andout of air reservoirs. These valves can be electronically controlledsilicon micro valves configured to provide optimal pressure and flow.FIG. 5E shows a remotely located stack configuration which provides airvia an air tube to a heat source. The air tube can be bifurcated toprovide more than one air flow direction to the heat source.

In some embodiments, a cooling unit can be attached to a pressurereservoir, as shown in FIG. 5B. The cooling unit can be provide a liquidrefrigerant to the one or more walls of the pressure reservoir, to coolpressurized air therein. Commercially available CPU cooling units can beimplemented in this manner such that the stack can provide impingementcooling at a temperature lower than ambient air temperature.

FIG. 5F shows a rear view of a TCD 500 with pluralities of linkedpressurized air sources (“stacks”)(501, 502, 503, 504) in use. Thearrangement of the stacks is in a similar manner to what is shown inFIG. 2C.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a number ofmodifications, changes, and adaptations may be implemented. Further, anydimensions mentioned are exemplary guidelines for one skilled in theart, and thus do not represent limitations as to size and/or proportionof the invention.

What is claimed is:
 1. A thermal cycling apparatus comprising: amounting wall partially defining a chamber for thermally cyclingbiological samples, the mounting wall having a first mounting surfaceopposing a second mounting surface; a sample interfacing walltransversely extending from the second mounting surface within thechamber, the sample interfacing wall having a planar interfaceaccessible from the first mounting surface, the sample interfacing wallhaving a first heating element and a second heating element on opposingsides of the planar interface; a first air source within the chamber andhaving an exit arranged to direct air at the first heating element; asecond air source disposed within the chamber and having an exitarranged to direct air away from the first heating element; a third airsource disposed within the chamber and having an exit arranged to directair at the second heating element; and a fourth air source disposedwithin the chamber and having an exit arranged to direct air away fromthe second heating element.
 2. The apparatus of claim 1, wherein eachair source comprises an air pump having a planar face, the exit being onthe planar face, and a plurality of edges surrounding the planar face.3. The apparatus of claim 2, wherein each air pump is coupled to thesecond mounting surface such that its planar face is transverse to thesecond mounting surface.
 4. The apparatus of claim 2, wherein the firstair pump, second air pump, and sample interfacing wall are arranged todefine a first sub-volume of the chamber.
 5. The apparatus of claim 4,wherein the exit of the second air pump is arranged to push air out ofan exit of the first sub-volume.
 6. The apparatus of claim 4, whereinthe third air pump, fourth air pump, and sample interfacing wall arearranged to define a second sub-volume of the chamber.
 7. The apparatusof claim 6, wherein the exit of the fourth air pump is arranged to pushair out of an exit of the second sub-volume.
 8. The apparatus of claim1, wherein the first and third air sources are each arranged to directrespective air streams directly at the first and second heatingelements.
 9. The apparatus of claim 8, wherein the second and fourth airsources are each arranged to direct an air stream at the sampleinterfacing wall.
 10. The apparatus of claim 8, wherein the second andfourth air sources are each arranged to direct an air stream along thesample interfacing wall.
 11. The apparatus of claim 10, wherein thesecond and fourth air sources are each arranged to suction air away fromthe sample interfacing wall.
 12. The apparatus of claim 1, wherein themounting wall and sample interfacing wall comprise printed circuitboards.
 13. The apparatus of claim 1, wherein the sample interfacingwall divides the chamber into equal volumes.
 14. The apparatus of claim13, wherein the air sources are symmetrically positioned about thesample interfacing wall.
 15. The apparatus of claim 1, wherein each airsource comprises a planar housing having an internal piezoelectricelement mounted to an internal diaphragm.
 16. The apparatus of claim 15,wherein each planar housing includes an exit port, and wherein the exitports of the first and third air sources are arranged to directlyprovide respective air streams at the first and second heating elements.17. The apparatus of claim 16, wherein the exit ports of the second andfourth air sources are arranged to provide respective air streams alongor away from the sample interfacing wall.
 18. The apparatus of claim 15,wherein the first, second, third and fourth air sources include a firstand second plurality of linked air pumps, wherein at least one of thefirst and second plurality of linked air pumps comprises a firstproximal air pump and a distal air pump, the outlet of the first airpump being fluidly coupled to the inlet of the distal air pump.
 19. Theapparatus of claim 18, wherein an outlet of a second proximal air pumpis fluidly coupled to the inlet of the distal air pump.
 20. Theapparatus of claim 19, wherein the first and second proximal pump arefluidly coupled in parallel.
 21. The apparatus of claim 19, wherein thefirst and second proximal pump are fluidly coupled in series.